A variety of printing systems, e.g., printers, copiers, facsimile (fax) machines and multifunction devices, utilize ink as a marking material. The ink is contained in ink reservoirs often referred to as cartridges. The ink is a liquid, and often an aqueous liquid.
As the printing system deposits the ink on print media, the level of ink in the cartridge will drop, eventually falling to a level where ink can no longer be delivered from the cartridge. At this point, the cartridge is deemed to be “empty” even though there is generally some quantity of ink retained in the cartridge.
It is generally advantageous to know when an ink cartridge is close to being empty in order to give a consumer or other end user an opportunity to purchase a fresh cartridge. Additionally, operation of a printer with a depleted ink supply may lead to loss of important information. For example, a printing system printing a facsimile message may receive the transmitted information and operate as if the received information is being printed. If the ink is depleted, the information is never printed. Unless the receiver can ask the sender to retransmit the fax, the information is irretrievable.
Knowing the relative ink level of the ink cartridge may be important under other considerations. For instance, before beginning a large print job, it would be useful to know the likelihood that the remaining ink is sufficient to finish the print job. If the amount of ink is insufficient, the ink cartridge can be replaced or replenished before it reaches its empty state in order to avoid wasting time, paper, and effort of unsuccessfully attempting to print the large print job.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative methods and apparatus for indicating ink level within an ink reservoir for use in a printing system.